Public servants may be tightening their belts, but they are still taking twice as many sick days as the rest of us.

Figures from the State Services Commission show government employees took an average of 7.6 sick days in 2012.

No official figures are kept for private sector sick leave, but an Employers and Manufacturers Association survey suggests the average could be as low as 3.7 days a year.

Association employment services manager David Lowe said the survey of 472 businesses, published earlier this year, showed the average number of sick days taken last year dropped from 5.3 the year before.

The discrepancy of nearly four days between public and private sector workers could be explained by a more relaxed public "workplace culture", he said.

"There is an impression that the workplace culture in the public sector might not be as focused as in the private sector."

But State Services Commissioner Iain Rennie said the numbers were not comparable, and noted that the association's survey reflected only a limited number of businesses that chose to participate.

The number of sick days in the public sector had remained relatively constant during the past three years, despite a stronger emphasis on not coming to work while sick, he said.

The Social Development Ministry was the sickliest government agency, with an average of 9.2 days off per person across its staff of more than 9000.

Inland Revenue workers also suffered more than their fair share of illness, with an average of 9.1 days a year. The Pacific Island Affairs Ministry, with just 40 staff, took an average of 8.4 sick days per person this year.

Social Development Ministry deputy chief executive Marc Warner said the number of sick days had dropped steadily in the past three years. The high number reflected the many staff who were interacting regularly with the public.

"Sick leave use in operational environments . . . is typically higher than that displayed in policy and national office environments."

At Inland Revenue, sick days were highest among frontline staff.

A Pacific Island Affairs Ministry spokeswoman said many of its staff had responsibilities for extended family, and took sick days to care for poorly relatives.

"Our ministry endeavours to be a good employer, which includes having a family-friendly approach to staff members' personal and family situations."

The State Services Commission was the healthiest government department, closely followed by the Serious Fraud Office, with workers taking an average of fewer than two days' sick leave.

Employers are legally required to give staff at least five days' sick leave but some government departments are more generous. The Pacific Island Affairs Ministry offers 10 days, and Inland Revenue 15.

Overall, the number of public servants has dropped by nearly 1400 in the past three years.